Im confused and need help

I plan to visit japan in August for 10 days and from what ive heard and read having a JRP is cheaper than trying to run normally which is fine my problem is when reading info on site it says that in order to use JRP you need a sightseeing visa... as im coming from the UK getting to japan doesnt need a visa are they one in the same or different cause im confused and trying to ger everything sorted before that time?